Ground station antennas that are designed to track non-geostationary satellites in mid-earth orbits (or medium earth orbits) (MEO) are often high-gain parabolic reflector-type antennas. Parabolic reflectors provide narrow beam widths and higher gain, and are pointed to maintain communication with the satellites. Movement of the reflector may be performed with expensive and complex mechanically-driven gimbaled systems that perform movement of a large and heavy antenna dish structure.
Because of the orbital dynamics of MEO satellites, simultaneous communication with two satellites provides uninterrupted service. As one satellite leaves the field of view of the ground station, another satellite enters the field of view. This often results in a system using two complex and expensive gimbaled reflector systems. A similar approach uses a fixed phased array antenna; however, the cost and complexity of the beam forming electronics to steer the beams is expensive and complicated. In addition, for fixed phase array antenna solutions, the beam pattern shape distorts or broadens as the beam is scanned away from the bore sight direction, making it difficult to meet pattern specifications for satellite communication (SATCOM) earth station antennas levied by various regulatory bodies such as the Federal Communications Commission (FCC) or the International Telecommunications Union (ITU).